The long term goal of this research is to develop quantitative optical imaging methods bioenergetic studies of tissue. In this proposal, methods will be developed for the optical determination of tissue or circulatory oxygen concentration based on palladium porphyrin phosphorescence quenching by collisional interaction with molecular oxygen. During Phase I of this project palladium porphyrins will be synthesized and software developed to produce and evaluate tissue oxygen images. This calibration of porphyrin phosphorescence with tissue oxygen concentration will be used to demonstrate the feasibility of using a videofluorometer to construct epicardial oxygen concentration images which will then be compared to images of epicardial NADH fluorescence. Phase II will: (1) assess the utility of monitoring phosphorescence decay kinetics to improve oxygen concentration imaging, (2) determine the distribution of different porphyrin compounds between vascular and epicardial tissue regions and (3) produce a videofluorometer capable of obtaining sequential NADH and palladium porphyrin images. This dual function videofluorometer will allow rapid, sequential imaging of tissue metabolism and oxygen concentration and will therefore have much greater utility in spatialluy quantifying tissue metabolism and oxygen supply/demand for research and clinical purposes than do current devices.